I approach lighting like any other problem. First I define a goal. Then I determine what strategies will achieve that goal. Finally I determine what tools and tactics are needed to implement the strategies. Not an original concept. Sun Tzu invented it about 3000 years ago.

The #1 goal in a conventional portrait is to flatter the subject and attract the viewer to the face in the photo. But on an even more fundamental, perceptual level the goal is to create the desired emotional reaction in the mind of the viewer.

The first strategy needed is to help the viewer find the FRONT of the face in the photo. That's done with contrast and by eliminating distractions. If the face contrasts strongly with everything else - background, clothing, props - then it will attract the eye like steel to a magnet; the stronger the contrast the more effective it will be attracting and holding the viewer. Notice the emphasis on front of the face. That's where the eyes and mouth which reveal mood and character are located.

The easiest way to create contrast between the front of the face and everything else is to eliminate the biggest potential distraction: clothing which contrasts more with the background than the face does. So if your portrait subject walks in wearing a white shirt or dress the first strategic decision should be to find a background which will blend in with the shirt and make it less distracting. Dark clothing? A background which is almost as dark will still provide needed foreground / background separation while making the face the star of the show by virtue of contrast. Bright colors like red can be very distracting, but if you put a red dress on a red background the dress will recede from consciousness and the face will contrast.

Lighting in the holistic sense isn't so much about where it put the light, but rather how to create a pattern of contrast which makes what is most important in the image the natural "steel to magnet" focal point for the viewer's eye. Just consider any other scenario where the most visually compelling area of contrast isn't your intended center of interest, such as when you have a face on a dark background with wearing a white shirt. Sure the viewer will find the face since making eye contact is an ingrained instinct proven by eye motion studies, but it will soon be distracted by that other contrasting stuff -- the distractions.

Want a compelling portrait?

1) Make the front of the face contrast with the background and clothing. Clothing should blend into the background so it does not compete for attention with the face (e.g. white shirt on dark background).

2) Make the eye and mouth "mask" area on the face contrast most with the rest of the face (side of head, ears, forehead, etc.

3) Hide the nose shadow. The nose shadow is the biggest potential distraction in a portrait. It's job is to define the shape of the nose in a realistic flattering way, not create a dark distraction hanging out sideways onto the brightly lit cheek next to it. Remember CONTRAST attracts attention and that kind of attention isn't good.

Hiding the nose shadow is the hardest thing to master because no two faces or noses are the same shape. That's why I think trying to learn lighting by copying patterns like Rembrandt, loop, etc. is a huge waste of time. It's more important to recognize what looks flattering for each person and facial type and what doesn't. That's done by changing the orientation of the face to the key light and seeing where the nose shadow goes in response. When it winds up somewhere the nose looks good and doesn't distract from the more important eyes and mouth it will usually be the most flattering lighting pattern and it really doesn't matter what it is called, besides "effective" for that face.

We don't need a set of studio lights to learn how to read and light faces. We can do it in the checkout line at Walmart, work, the mall, etc. TV interviews are also very good way to observe lighting. The lights are usually set so the host and subject are both in perfect short lit oblique poses because it is the most flattering combination for most people. But then as the people move their heads out of that perfect configuration it is very easy to see how slight changes in facial angle and lighting radically change the appearance of the face.

Just stop and look at the person profile-to-profile before photographing them. Pay particular attention to the precise full-face (two equal ears), oblique (one ear), and profile (clean like a penny) views because they are the most naturally flattering. By looking at all five views before shooting you will know which of them is the most flattering. Then its just a matter of selecting a background which will match the clothing so it will not compete with the face, then finally picking the lighting style which will best contrast the face on that background.

Pretty simple when you look at the problem of lighting that way isn't it?